1. Field of the Invention
The present invention relates to a wire-driving system which is utilized in various machines, such as a copying machine, an image scanner, a facsimile machine, a printer and so on, to drive and move a movable unit along a guide path. Also, the present invention relates to an image reader including an elongated image scanner unit which is moved by such a wire-driving system.
2. Description of the Related Art
Conventionally, a basic principle of such a wire-driving system resides in traction or pulling of a movable unit with a wire cable. For example, in order to pull and move the movable unit along a guide path, the wire-driving system includes a pair of pulleys provided at the terminal ends of the guide path, and an endless wire cable entrained by and stretched between the pulleys, with a part of the endless wire cable being securely attached to the movable unit. One of the pulleys functions as a drive pulley operationally connected to an electric drive motor, and thus it is possible to move the movable unit along the guide path by rotationally driving the drive pulley with the electric drive motor.
Accordingly, before the wire-driving system can be assembled in a machine, such as a copying machine, an image scanner, a facsimile machine, a printer or the like, a wide space for accommodating the wire-driving system has to be prepared in the machine, resulting in a bulky construction of the machine due to the arrangement of the pulleys, the electric drive motor and so on.
A wire-drive system is frequently used in a copying machine to drive an optical scanning unit along a pair of parallel guide rails, as disclosed in Japanese Laid-Open Patent Publications (KOKAI) No. SHO-60-114848 and No. HEI-02-146861. In general, the optical scanning unit has an elongated configuration, and is laid across the pair of parallel guide rails. Thus, in order for the elongated optical scanning unit to be stably and smoothly moved along the parallel guide rails, the elongated optical scanning unit must be pulled at the ends thereof, using two endless wire cables. Namely, it is necessary to arrange the respective endless wire cables along the guide rails, and further the endless wire cables have to be synchronously driven to ensure the stable and smooth movement of the elongated optical scanning unit along the guide rails.
Thus, the machine, using the wire-driving system for driving the elongated movable unit, necessarily becomes more bulky and complicated.
Therefore, an object of the present invention is to provide a wire-driving system which can be compactly and simply arranged in various machines, such as a copying machine, an image scanner, a facsimile machine, a printer and so on, to drive and move a movable unit along a guide path.
Another object of the present invention is to provide a wire-driving system which can be compactly and simply arranged in a machine including an elongated movable unit, such as a copying machine, an image scanner, a facsimile machine, a line printer or the like, to stably and smoothly drive and move the elongated movable unit along a wide guide path.
Yet another object of the present invention is to provide an image reader including an elongated image scanner unit which is moved by such a wire-driving system, whereby the image reader can be compactly constructed.
In accordance with a first aspect of the present invention, there is provided a wire-driving system that drives and moves a movable unit along a guide path. The wire-driving system comprises a drive drum member rotatably provided on the movable unit so as to be rotated around a rotational axis which is perpendicular to a movement direction of the movable unit, a drive source provided in the movable unit and operationally connected to the drive drum member so as to be rotationally driven in either a first rotational direction or a second rotational direction, and a wire cable having a first end and a second end, and partially wound around the drive drum member such that a first cable section and a second cable section are extended from the drive drum member. The respective first and second ends of the wire cable are securely attached to two fixed points beside terminal ends of the guide path such that the first and second cable sections of the wire cable are tensionally extended along the guide path. The respective first and second cable sections of the wire cable are wound around and unwound from the drive drum member during the rotation of the drive drum member in the first rotational direction by the drive source, and the respective first and second cable sections of the wire cable are unwound from and wound around the drive drum member during the rotation of the drive drum member in the second rotational direction by the drive source, resulting in the movement of the movable unit along the guide path.
Preferably, the wire cable is securely attached to the drive drum member at a middle point between the first and second ends of the wire cable such that the respective first and second cable sections are defined as respective ones extending from the middle point to the first and second ends of the wire cable, the respective first and second cable sections of the wire cable being wound around the drive drum member in reverse directions with respect to each other.
A movement range, in which the movable unit is moved along the guide path, may be equivalent to a length of the winding turns of the wire cable around the drive drum member.
In accordance with a second aspect of the present invention, there is provided a wire-driving system that drives and moves an elongated movable unit along a guide path defined by a first side and a second side opposite to each other. The wire-driving system comprises a drive drum member rotatably provided on a first end of the elongated movable unit so as to be rotated around a rotational axis which is perpendicular to a movement direction of the elongated movable unit, a drive source provided in the elongated movable unit and operationally connected to the drive drum member so as to be rotationally driven in either a first rotational direction or a second rotational direction, a first wire cable having a first end and a second end, and partially wound around the drive drum member such that a first cable section and a second cable section are extended from the drive drum member, and a second wire cable having a first end and a second end, and partially wound around the drive drum member such that a first cable section and a second cable section are extended from the drive drum member. The first end of the first wire cable and the second end of the second wire cable are securely attached to two fixed points beside terminal ends of the first side of the guide path such that the first cable section of the first wire cable and the second cable section of the second wire cable are tensionally extended along the first side of the guide path. The wire-driving system further comprises a wire-cable deflector provided on a second end of the elongated movable unit such that the second cable section of the first wire cable and the first cable section of the second wire cable are threaded through the wire-cable deflector so as to laterally traverse the guide path, whereby the second end of the first wire cable and the first end of the second wire cable are securely attached to two fixed points beside ends of the second side of the guide path such that the second cable section of the first wire cable and the first cable section of the second wire cable are tensionally extended along the second side of the guide path. Both the first cable sections of the first and second wire cables and both the second cable sections of the first and second wire cables are respectively wound around and unwound from the drive drum member during the rotation of the drive drum member in the first rotational direction by the drive source, and both the first cable sections of the first and second wire cables and both the second cable sections of the first and second wire cables are respectively unwound from and wound around the drive drum member during the rotation of the drive drum member in the second rotational direction by the drive source, resulting in the movement of the elongated movable unit along the guide path.
Preferably, the first wire cable is securely attached to the drive drum member at a middle point between the first and second ends of the first wire cable such that the first and second cable sections are defined as respective ones extending from the middle point to the first and second ends of the first wire cable, and the respective first and second cable sections of the first wire cable are wound around the drive drum member in reverse directions with respect to each other. Also, preferably, the second wire cable is securely attached to the drive drum member at a middle point between the first and second ends of the second wire cable such that the first and second cable sections are defined as respective ones extending from the middle point to the first and second ends of the second wire cable, and the respective first and second cable sections of the second wire cable are wound around the drive drum member in reverse directions with respect to each other.
A length of the winding turns of the first wire cable may be equal to that of the winding turns of the second wire cable. In this case, a movement range, in which the elongated movable unit is moved along the guide path, is equivalent to the length of the winding turns of each wire cable around the drive drum member.
Preferably, the wire-cable deflector comprises first and second pulleys, each of which is rotatable around a rotational axis parallel with the rotational axis of the drive drum member, and a third pulley which is rotatable around a rotational axis perpendicular to the rotational axis of the drive drum member. The second cable section is threaded through the first and third pulleys, and is deflected such that the end of the second cable section is securely attached to the corresponding fixed point. The first cable section is threaded through the second and third pulleys, and is deflected so as to be wound around the drive drum member.
Preferably, the first and second wire cables are orderly wound around the drive drum member such that the winding and unwinding of the first wire cable and the winding and unwinding of the second wire cable do not interfere with each other. In this case, both the first cable sections of the first and second wire cables may be wound around the drive drum member such that the winding turns of first cable sections are shifted in one direction along the rotational axis of the drive drum member, and both the second cable sections of the first and second wire cable may be wound around the drive drum member such that the winding turns of the second cable section are shifted in a reverse direction along the rotational axis of the drive drum member. With the arrangement, the two adjacent cable sections of the first and second wire cables can be wound around and unwound from the drive drum member when the drive drum member is driven in the first rotational direction, and the two adjacent cable sections of the first and second wire cables can be unwound from and wound around the drive drum member when the drive drum member is driven in the second rotational direction.
In accordance with a third aspect of the present invention, there is provided an image reader which comprises an elongated image scanner unit that is movable along a guide path defined by a first side and a second side opposite to each other, a drive drum member rotatably provided on a first end of the elongated image scanner unit so as to be rotated around a rotational axis which is perpendicular to a movement direction of the elongated image scanner unit, a drive source provided in the elongated image scanner unit and operationally connected to the drive drum member so as to be rotationally driven in either a first rotational direction or a second rotational direction, a first wire cable having a first end and a second end, and partially wound around the drive drum member such that a first cable section and a second cable section are extended from the drive drum member, a second wire cable having a first end and a second end, and partially wound around the drive drum member such that a first cable section and a second cable section are extended from the drive drum member. The first end or the first wire cable and the second end of the second wire cable are securely attached to two fixed points beside terminal ends of the first side of the guide path such that the first cable section of the first wire cable and the second cable section of the second wire cable are tensionally extended along the first side of the guide path. The image reader further comprises a wire-cable deflector provided on a second end of the elongated image scanner unit such that the second cable section of the first wire cable and the first cable section of the second wire cable are threaded through the wire-cable deflector so as to laterally traverse the guide path, and the second end of the first wire cable and the first end of the second wire cable are securely attached to two fixed points beside ends of the second side of the guide path such that the second cable section of the first wire cable and the first cable section of the second wire cable are tensionally extended along the second side of the guide path. Both the first cable sections of the first and second wire cables and both the second cable sections of the first and second wire cables are respectively wound around and unwound from the drive drum member during the rotation of the drive drum member in the first rotational direction by the drive source, and both the first cable sections of the first and second wire cables and both the second cable sections of the first and second wire cables are respectively unwound from and wound around the drive drum member during the rotation of the drive drum member in the second rotational direction by the drive source, resulting in the movement of the elongated image scanner unit along the guide path.
Preferably, the image reader further comprises a pair of guide rails on which the elongated image scanner unit is slidably mounted, such that the elongated image scanner unit is movable along the guide path.